docs: def render_flags(flags, bit_list):
      """Show bit names.
      """
      res = []
      known = 0
      for bit in bit_list:
          known = known | bit[0]
          if flags & bit[0]:
              res.append(bit[1])
      unknown = flags & ~known
      n = 0
      while unknown:
          if unknown & 1:
              res.append("UNK_%04x" % (1 << n))
          unknown = unknown >> 1
          n += 1
  
      if not res:
          return '-'
  
      return ",".join(res)